RU2327114C2 - Method of determination of levels difference and flow rate of water on open current with prismatic riverbed by method of incline-area - Google Patents

Abstract

FIELD: technological processes; measurement.

SUBSTANCE: invention is related to the sphere of hydrometry and may be used in the system of water distribution and accounting on open currents with prismatic riverbed. The substance of method consists in use of one level meter, which is installed in level metering well of lower hydrometric station, for measurement of levels in upper and lower hydrometric stations, determination of levels difference between upper and lower stations and calculation of flow rate. It provides the possibility to significantly reduce inaccuracy of levels difference determination (by 50%). Level metering well allows excluding the water level pulsation, which also increases accuracy of measurement.

EFFECT: increase of accuracy of levels difference and water flow rate determination.

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Description

The invention relates to the field of hydrometry and can be used in a system of water distribution and water metering in open streams with a prismatic channel.

A device for determining the slope of the free surface of watercourses / 1 /, the operation of which is based on the use of a differential pressure gauge to measure the difference in hydrostatic pressures (level difference), which can be used to determine the slope.

The disadvantages of the device are the inability to use irrigation systems on open channels, the inability to determine the depth of flow.

The closest technical solution is the method of determining the flow rate / 2 /, which includes a measuring section of the channel (with a reverse slope i _arr = - (0.001-0.003), length L = (00-25) b, where b is the width of the channel along the bottom) with variable slopes and two depth gauges, spaced from each other at a distance L ₁ = (10-15) b.

The disadvantage of this method is the use of two depth gauges, which leads to a doubling of the error in measuring the level difference, there is a pulsation of levels in an open watercourse, which worsens the accuracy of measuring depth, the inability to automate the measurement process, and a reverse slope device that contributes to siltation of the channel.

The objective of the present invention is to improve the accuracy of determining the flow rate of water in an open stream with a prismatic channel.

This is achieved by using a single level measuring device for measuring levels in the upper and lower hydrometric gauges, which makes it possible to significantly reduce the level measurement error, the level gauge well eliminates fluctuations in the water level, which also increases the accuracy of the measurement.

In the initial channel, a lined section with a length of L = 40 m is performed. The distance between two sections in the section L is chosen equal to l _shaft = (20-30) m. Water levels in these sections are measured with one electronic level gauge with an absolute level measurement error of 0.1 mm located in the level gauge well of the lower gauge alignment. Measurement of water levels in the upper and lower sections is based on the principle of two communicating vessels with alternating automatic switching of the connection of the level gauge well with the watercourse of the upper and lower hydrometric sections.

The electronic level gauge works according to the program and carries out the functions of collecting and processing information, as well as controlling the actuator (shut-off valve).

The connection of the level gauge well with a diameter of at least 300 mm with the zones of the hydrometric gauges is carried out using pipes with a diameter of at least 50 mm.

The measuring section of the channel (Fig. 1) consists of a measuring channel 1, a supply pipe 2 from the zone of the upper gauge, a shutoff valve 3, a level gauge 4, a level gauge well 5 and a supply pipe 6 from the zone of the lower gauge.

The sequence of operations when determining the flow rate according to the proposed method is as follows (figure 1, 2). The shutoff valve 3 opens the water flow between the inlet pipe 2 and the level gauge well 5. Upon completion of filling the level gauge well 5, the first indication of the level gauge 4 (h ₁ ) is recorded. Then, the shutoff valve 3 closes the flow between the level gauge well 5 and the supply pipe 2, opens the flow between the level gauge 5 and the supply pipe 6, while the water in the level gauge 5 decreases to the surface level of the water of the lower gauge section. At the end of the level change, the second reading of the level gauge 4 (h ₂ ) is recorded.

From the obtained data and with known parameters of the channel (the distance between the sections of the upper and lower hydrometric sections of l _channels , the slope of the channel bottom i ₀ , the roughness coefficient of the channel n, the channel width along the bottom b, the coefficient of slope m, etc.), the coefficient values Shesi C and hydraulic radius R / 3 /. Substituting the found and known values in the formula (1), calculate the desired flow rate Q.

The required flow rate is calculated by the formula (1), which is a solution to the ordinary differential equation of the non-uniform steady-state smoothly changing water flow in the open channel / 3 /, converted to the form

where Q is the flow rate, m ³ / s;

Δh is the determined difference in water levels between the upper and lower hydrometric gauges, m;

k is a certain number that determines the step of integration;

α is the velocity coefficient equal to 1.1;

B is the width of the channel along the free surface of the water, m;

g is the acceleration of gravity, m / s ² ;

w is the living cross-sectional area of the stream in the lower section, m ² ;

l _STV - distance between sections, m;

i ₀ - the slope of the bottom of the channel;

C - Shezy coefficient in the lower section, m ^0.5 / s;

R is the hydraulic radius in the lower alignment, m

This method of measuring water flow provides:

- improving the accuracy and reliability of determining the flow rate due to more accurate measurement of the difference in water levels (by 50%) in the upper and lower measuring sections, because measurements are made by one measuring device (level gauge);

- the ability to automate the measurement process;

- the possibility of reducing the value of the reverse slope or a complete rejection of the reverse slope device;

- reducing the cost of operating the measuring section due to the proximity of the hydrometric gauges and the lack of need for the construction of a second level gauge well.

Claims (1)

A method for determining water flow in an open watercourse with a prismatic channel, including measuring levels in two sections of the channel with subsequent calculation of the flow by the difference in levels in these sections with known channel parameters, characterized in that the levels in the upper and lower hydrometric sections of the channel are made using one level gauge located in the level gauge well of the lower gauge alignment, and the flow rate Q is calculated by the formula

where Q is the flow rate m ³ / s; Δh is the determined difference in water levels between the upper and lower hydrometric gauges, m; k is a certain number that determines the step of integration; α is the velocity coefficient equal to 1.1; B is the width of the channel along the free surface of the water, m; g is the acceleration of gravity, m / s ² ; w is the living cross-sectional area of the stream in the lower section, m; l _stem - the distance between the sections, m; i ₀ - the slope of the bottom of the channel; C - Shezy coefficient in the lower section, m ^0.5 / s; R is the hydraulic radius in the lower alignment, m

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